According to current estimations, unconventional heavy oils recoverable reserves alone can satisfy the global demand for 20 years. The development of reliable and economic in-situ extraction technologies is considered to be the key point to unlock the potential of great amounts of hydrocarbon reserves such as those located in the oil sands of Alberta, Canada and the extra heavy oils in the Orinoco Belt of Venezuela.
The mechanism of some existing solutions is deemed to be proven, but the energy requirements of existing technologies are too high to be economical, and none of this technology is really mature enough for companies to be willing to make substantial investments in them.
Existing extraction technologies include Steam Assisted Gravity Drainage (SAGD), which is a steam flooding technique improved by the use of two horizontal wells. One of these wells is for steam injection and the other is for bitumen extraction. The steam heats the formation, increasing the viscosity of the bitumen, which can now flow to the producer. The main drawbacks concern high SOR (steam to oil ratio), which can range from 1.8 to 4.0. The performance of SAGD are strictly dependent upon the reservoir properties and characteristics such as gas caps, aquifers and any shale that may be present in the reservoir. These criteria can result in a potential operation scenario that is not economic. The use of steam alone is deemed to result in a bigger vertical propagation of the steam chamber, potentially resulting in a more pronounced gas over bitumen extraction.
Another existing technology is Vapor Extraction (VE), which involves injecting a gaseous hydrocarbon solvent into the reservoir where it dissolves into the bitumen, which becomes less viscous and can drain into a lower horizontal well and be extracted. The solvent is typically propane, butane or even carbon dioxide along with a carrier gas. The main drawbacks of this technique is that the blending of the oil with the solvent, without heating the formation, produces only small improvements in oil recovery. Also, the solvent is expensive, scarce, and losses in the reservoir can be economically important.
There are also hybrid processes such as ES-SAGD, LASER, or SAVEX (see U.S. Pat. No. 6,662,872), which are currently under development in order to provide a hybrid in-situ extraction technology that couples the advantages of steam (i.e. thermal reduction of oil viscosity) and solvent injection. Light hydrocarbons are used and solutions to drawbacks such as reservoir depressurization and solvent losses have to be provided for. None of these hybrid processes have managed to combine the advantages of thermal extraction with miscible and immiscible flooding